1. Technical Field
The present invention relates both to a method for fuel transfer in combustion engines including resupply of return fuel to the engine, and to an arrangement for fuel transfer in combustion engines, including a second fuel tank to receive return fuel from the engine and supply it to the engine in addition to fuel from a first fuel tank.
2. State of the Art
In combustion engines of various kinds it is usual for fuel to be drawn from a fuel tank to the engine and for any excess fuel to be returned to the fuel tank. This entails the possibility of dirt; air, gas and heat also reaching the fuel tank, which may result in various kinds of problems. In particular, in cases where a diesel engine is provided with fuel injectors which are intended to be constantly open, there is a large return flow of fuel which is very hot and contains a great deal of air. The high return fuel temperature may make it necessary to use heat-tolerant material, e.g. steel, for the fuel tank instead of, for example, plastic. Another type of problem is that long fuel lines may make it difficult to meet essential positive and negative pressure requirements with respect to the fuel pump situated adjacent to the engine. Moreover, too much air in return fuel can cause excessive pressure in the fuel tank, and further possible problems can be caused by dirt accumulation in the fuel tank.
Returning excess fuel to the fuel tank may result in a flowmeter situated in the fuel line from the fuel tank not providing sufficiently accurate information about the engine's fuel consumption, since the return flow makes accurate measurement of fuel consumption difficult. An attempt to solve this problem is referred to in GB 1 433 875 whereby return fuel is gathered in an extra fuel tank which can be connected, when it reaches a sufficient fuel level, to the ordinary suction line between the fuel tank and the engine. This arrangement makes it possible for a flowmeter fitted close to the fuel tank to monitor fuel consumption with good accuracy, since return fuel does not reach the fuel tank. Even so, various problems may still arise, e.g. with regard to high pressure in fuel tanks or to long fuel lines and appropriate pressure at the fuel pump.
Against this background, there is a need for better solutions in this respect with a view to achieving; for example, greater operational reliability and simpler installation, particularly in cases where there is a large return flow of fuel.